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    <title>Document</title>
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<body>
    <script>
        function isNumber(a){
            if(!isNaN(a)){
                console.log(a,"是纯数字")
            }
            else{
                console.log(a,"不是纯数字")
            }     
        }
        // var a = "66622"
        isNumber("3333")
    </script>
</body>
</html>